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Bojić MG, Treven M, Pandey KP, Tiruveedhula VVNPB, Santrač A, Đukanović Đ, Vojinović N, Amidžić L, Škrbić R, Scholze P, Ernst M, Cook JM, Savić MM. Vascular effects of midazolam, flumazenil, and a novel imidazobenzodiazepine MP-III-058 on isolated rat aorta. Can J Physiol Pharmacol 2024; 102:206-217. [PMID: 37909404 DOI: 10.1139/cjpp-2023-0285] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2023]
Abstract
Hypotensive influences of benzodiazepines and other GABAA receptor ligands, recognized in clinical practice, seem to stem from the existence of "vascular" GABAA receptors in peripheral blood vessels, besides any mechanisms in the central and peripheral nervous systems. We aimed to further elucidate the vasodilatatory effects of ligands acting through GABAA receptors. Using immunohistochemistry, the rat aortic smooth muscle layer was found to express GABAA γ2 and α1-5 subunit proteins. To confirm the role of "vascular" GABAA receptors, we investigated the vascular effects of standard benzodiazepines, midazolam, and flumazenil, as well as the novel compound MP-III-058. Using two-electrode voltage clamp electrophysiology and radioligand binding assays, MP-III-058 was found to have modest binding but substantial functional selectivity for α5β3γ2 over other αxβ3γ2 GABAA receptors. Tissue bath assays revealed comparable vasodilatory effects of MP-III-058 and midazolam, both of which at 100 µmol/L concentrations had efficacy similar to prazosin. Flumazenil exhibited weak vasoactivity per se, but significantly prevented the relaxant effects of midazolam and MP-III-058. These studies indicate the existence of functional GABAA receptors in the rat aorta, where ligands exert vasodilatory effects by positive modulation of the benzodiazepine binding site, suggesting the potential for further quest for leads with optimized pharmacokinetic properties as prospective adjuvant vasodilators.
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Affiliation(s)
- Milica Gajić Bojić
- Faculty of Medicine, Center for Biomedical Research, University of Banja Luka, Banja Luka 78000, Republic of Srpska, Bosnia and Herzegovina
| | - Marco Treven
- Neurology Department, Medical University of Vienna, Vienna, Austria
| | - Kamal P Pandey
- Department of Chemistry and Biochemistry, Milwaukee Institute for Drug Discovery, University of Wisconsin-Milwaukee, Milwaukee, WI, USA
| | - V V N Phani Babu Tiruveedhula
- Department of Chemistry and Biochemistry, Milwaukee Institute for Drug Discovery, University of Wisconsin-Milwaukee, Milwaukee, WI, USA
| | - Anja Santrač
- Department of Pharmacology, Faculty of Pharmacy, University of Belgrade, Belgrade 11000, Serbia
| | - Đorđe Đukanović
- Faculty of Medicine, Center for Biomedical Research, University of Banja Luka, Banja Luka 78000, Republic of Srpska, Bosnia and Herzegovina
| | - Nataša Vojinović
- Faculty of Medicine, Center for Biomedical Research, University of Banja Luka, Banja Luka 78000, Republic of Srpska, Bosnia and Herzegovina
| | - Ljiljana Amidžić
- Faculty of Medicine, Center for Biomedical Research, University of Banja Luka, Banja Luka 78000, Republic of Srpska, Bosnia and Herzegovina
| | - Ranko Škrbić
- Faculty of Medicine, Center for Biomedical Research, University of Banja Luka, Banja Luka 78000, Republic of Srpska, Bosnia and Herzegovina
| | - Petra Scholze
- Department of Pathobiology of the Nervous SystemCenter for Brain Research, Medical University of Vienna, Vienna, Austria
| | - Margot Ernst
- Department of Pathobiology of the Nervous SystemCenter for Brain Research, Medical University of Vienna, Vienna, Austria
| | - James M Cook
- Department of Chemistry and Biochemistry, Milwaukee Institute for Drug Discovery, University of Wisconsin-Milwaukee, Milwaukee, WI, USA
| | - Miroslav M Savić
- Department of Pharmacology, Faculty of Pharmacy, University of Belgrade, Belgrade 11000, Serbia
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